Answer
$\frac{7b-2a}{ab}$.
Work Step by Step
In order to add or subtract fractions, we start by making a common denominator (bottom of the fraction). Thus, we multiply 7/a by b/b and 2/b by a/a to obtain:
$\frac{7b}{ab}$-($\frac{2a}{ab}$)=$\frac{7b-2a}{ab}$.
